Terrain awareness systems or TAWS are known which give alerts based on locations of aircraft with respect to terrain or point obstacles. Such systems are clearly useful for warning pilots of impending dangerous terrain. However, such systems fail to account for important factors, including that not all obstacles are represented in these systems. This may be particularly true for aircraft such as helicopters, which often fly at different and in particular lower altitudes than fixed-wing aircraft.
One reason for such deficiency is that, if obstacles were kept in a typical gridded database, which does not allow for discrete points, the obstacles would be considered at least as big as a grid square, e.g., 300 feet on a side, and in some cases as large as several grid squares (where an obstacle touches on the several grid squares, even if not fully occupying them).